Please Help Me!!!!

I'm very very new to having tropical fish and lots of people are telling me different stories about changing the water in my new fish tank, someone told me not to clean it because the tank matures by it's self because i have a under floor gravel system but others are telling me to clean the tank regulary but i'm scared that i'm killing my fish i've already lost 2 Neon Tetras.

Can someone please help me how i should clean the tank, i'm confused!!!!!!

Also 2 off my fish are behaiving very weird, the only way to describe it is they're shaking, is it because the waters not right and i need to get a water testing kit???

Welcome to FishLore! It's great to have you with us! What you are probably experiencing is either high ammonia or high nitrites or both. What you need to do first is understand the cycle process. Please read these beginner articles to get you started:

Next, we need to know more about your tank. What size is the tank, & how long has it been set up? What fish do you have in the tank? Do you have a master test kit? What are your ammonia, nitrite and nitrate readings?

We are so glad you decided to join us! You will not be ridiculed here, and if it happens, just let me know. We have some really great folks here that are dying to help you get your tank cycled, and looking beautiful. Your answers to the above questions will help us out a lot in doing this.